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 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
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REGION 8
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1595 Wynkoop Street
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Denver, CO   80202-1129
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Phone 800-227-8917
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www.epa.gov/region8


Ref: 8ARD-PM

Ms. Beth Stimatz
Environmental Compliance Specialist
NorthWestern Energy Corporation
11 East Park Street
Butte, Montana  59701

Re:	Application Incompleteness Determination for the Synthetic Minor New Source Review Permit SMNSR-B-000005-2022.003 NorthWestern Energy, Meriwether Compressor Station

Dear Ms. Stimatz:

The Environmental Protection Agency, Region 8, has completed its review of NorthWestern Energy Corporation's application for a synthetic minor permit in accordance with the Federal Minor New Source Review (MNSR) Permit Program in Indian Country at 40 CFR part 49 for a proposed modification at the existing Meriwether Compressor Station, located on the Blackfeet Indian Reservation in Glacier County, Montana. The EPA received the application on March 17, 2022. NorthWestern Energy is proposing to add one new 2,500 horsepower natural gas-fired compressor engine and is requesting synthetic minor restrictions to maintain allowable emissions for the facility below the major source thresholds of the Title V Operating Permit Program at 40 CFR part 71.

Pursuant to 40 CFR 49.154(b) and (d) and 49.158, we have determined that the information submitted in the application is incomplete and insufficient to begin evaluating and drafting a permit for the Meriwether Compressor Station. As discussed via emails dated April 13-14, 2022, based on the information provided in the application, our recommendation is that some modeling is necessary for the pollutants that would be emitted by the proposed project. We provided some guidance for modeling emissions in the project area. Bison Engineering, Inc. (Bison), as contracted by NorthWestern Energy, responded with a general description of the proposed modeling protocol and we recommended that Bison should work with our modeler, Rebecca Matichuk, to discuss the proposed modeling protocol before moving forward with modeling the proposed project emissions. As of May 13, 2022, we have not received any additional correspondence from Bison regarding the proposed modeling protocol.

The EPA is sending NorthWestern Energy this letter to document the incompleteness determination, remind NorthWestern Energy of its continuing obligation to correct any misinformation and provide updated information to the EPA or at the EPA's request, and to remind NorthWestern Energy of its continuing obligation to comply with all applicable permitting and regulatory requirements. At this time we are requesting that NorthWestern Energy either provide an Air Quality Impacts Analysis (AQIA) for the proposed project or contact Rebecca Matichuk to discuss a proposed protocol for an AQIA by May 17, 2022. If the requested information is not provided by the specified date and NorthWestern Energy has not contacted the EPA for consideration of a deadline extension, the permit application will be 

considered withdrawn, in which case, NorthWestern Energy would need to submit a new complete application to permit the proposed modification project.

This permit action has been assigned to Ms. Claudia Smith of my staff and has been given permit number SMNSR-B-000005-2022.003. If you have any questions, please contact her at smith.claudia@epa.gov or (303) 312-6520. A copy of the application provided by NorthWestern Energy may be reviewed electronically online through Docket #EPA-R08-OAR-2022-0345 at https://www.regulations.gov. We look forward to working with your company in preparing the synthetic MNSR permit.

							Sincerely,


							Monica S. Morales
							Acting Director
							Air and Radiation Division



Or if email:

Email to Permittee on incomplete application received for MNSR permit (copy Tribal Environmental Program Contact(s), Gail Fallon, and the NSR Permits Lead)

Subject Line: Incomplete Synthetic Minor NSR Application for Meriwether Compressor Station 

Beth,

This is to notify you that the EPA has completed its initial review of NorthWestern Energy Corporation's application for a synthetic minor permit in accordance with the Federal Minor New Source Review (MNSR) Permit Program in Indian Country at 40 CFR part 49 for a proposed modification to the existing Meriwether Compressor Station located on the Blackfeet Indian Reservation in XX County, Montana. The EPA received the application on March 17, 2022. NorthWestern Energy is proposing to add one new 2,500 horsepower natural gas-fired compressor engine and is requesting synthetic minor restrictions to maintain allowable emissions for the facility below the major source thresholds of the Title V Operating Permit Program at 40 CFR part 71.

Pursuant to 40 CFR 49.154(b) and (d) and 49.158, we have determined that the information submitted in the application is incomplete and insufficient to begin evaluating and drafting a permit for the Meriwether Compressor Station. As discussed via emails dated April 13-14, 2022, based on the information provided in the application, our recommendation is that some modeling is necessary for the pollutants that would be emitted by the proposed project. We provided some guidance for modeling emissions in the project area. Bison Engineering, Inc. (Bison), as contracted by NorthWestern Energy, responded with a general description of the proposed modeling protocol and we recommended that Bison should work with our modeler, Rebecca Matichuk, to discuss the proposed modeling protocol before moving forward with modeling the proposed project emissions. As of May 13, 2022, we have not received any additional correspondence from Bison regarding the proposed modeling protocol.

The EPA is sending NorthWestern Energy this email to document the incompleteness determination, remind NorthWestern Energy of its continuing obligation to correct any misinformation and provide updated information to the EPA or at the EPA's request, and to remind NorthWestern Energy of its continuing obligation to comply with all applicable permitting and regulatory requirements. We are requesting that NorthWestern Energy either provide an Air Quality Impacts Assessment (AQIA) for the proposed project or contact Rebecca Matichuk to discuss a proposed protocol for an AQIA by May 17, 2022. If the requested information is not provided by the specified date and NorthWestern Energy has not contacted the EPA for consideration of a deadline extension, the permit application will be considered withdrawn, in which case, NorthWestern Energy would need to submit a new complete application to permit the proposed modification project.

This permit action has been assigned to Ms. Claudia Smith of my staff and has been given permit number SMNSR-B-000005-2022.003. If you have any questions, please contact her at smith.claudia@epa.gov or (303) 312-6520. A copy of the application provided by NorthWestern Energy may be reviewed electronically online through Docket #EPA-R08-OAR-2022-0345 at https://www.regulations.gov. We look forward to working with your company in preparing the synthetic MNSR permit.

Thank you,

